Effect of cathode and electrolyte transport properties on chromium poisoning in solid oxide fuel cells

Fergus, Jeffrey W.

doi:10.1016/j.ijhydene.2006.08.005

Cited by 260 publications

(135 citation statements)

References 77 publications

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“…En la medida que la presión de vapor sea más alta en el aire, es más probable que ocurra el envenenamiento en el cátodo. Esta degradación, puede originar la reducción en el voltaje o aumento (más negativo) en el sobrepotencial de la celda 14,37 . En la figura 5, se ilustra el proceso de envenenamiento con Cr 38 .…”

Section: Selección De Materiales Metálicosunclassified

Avances en el desarrollo de interconectores metálicos de celdas SOFC

Alvarado-Flores¹

2013

Bol. Soc. Esp. Ceram. Vidr.

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INTRODUCCIÓNLas celdas de combustible son dispositivos de conversión de energía que producen electricidad de forma directa a partir de un combustible gaseoso por combinación electroquímica del combustible con un oxidante. La tecnología de las celdas de combustible de óxido sólido (SOFC), se ha convertido en un método cada vez más atractivo para la generación de energía, debido a sus bajas emisiones, flexibilidad en el combustible y alta eficiencia en comparación con los sistemas tradicionales de conversión de energía. Las principales aplicaciones de las celdas SOFC son: sistema estacionario de generación de energía, servir como unidad de potencia auxiliar (APU) y aplicaciones militares. La alta temperatura de funcionamiento en este tipo de celda, comparada a otros tipos de celdas de combustible (PEM, AFC, PAFC), las hace ideales para aplicarse en ciclos combinados SOFC/turbina de gas (GT), y así obtener una eficiencia entre 70-80 % 1 . El mecanismo fundamental del funcionamiento en una celda SOFC, es la oxidación de hidrógeno y otros combustibles en el ánodo, y la reducción de oxígeno en el cátodo, para crear una diferencia de potencial entre los dos electrodos. En función del combustible empleado, los productos de reacción pueden ser agua y CO 2 . La energía química se libera tanto en energía eléctrica, como en forma de calor a causa de las polarizaciones y pérdidas óhmicas 2 . Una celda SOFC, está compuesta de un electrolito, un ánodo y un cátodo. El electrolito, es un sólido cerámico no poroso, generalmente de ZrO 2 estabilizada con Y 2 O 3 (YSZ). La celda SOFC, opera a una temperatura entre 600 y1000 ºC, donde el electrolito cerámico es un conductor de iones de oxígeno, O 2-, pero no un conductor de electrones. La alta temperatura de operación, presenta algunas ventajas como minimizar las pérdidas de polarización y tolerancia del catalizador al envenenamiento por las impurezas en el combustible 3,4 . Generalmente, el ánodo está fabricado del cermet níquel-circona estabilizada con itria (Ni-YSZ) y el cátodo es un conductor electrónico tipo perovskita de Sr dopado con el cermet LaMnO 3 (LSM), además de otros materiales con estructura perovskita. EL INTERCONECTOR EN UNA CELDA SOFCIndividualmente, una celda SOFC, puede producir un voltaje o potencial alrededor de 1 V en circuito abierto El interés en las celdas de combustible de óxido sólido (SOFC), se deriva de su alta eficiencia y la capacidad de tener un bajo nivel de emisiones contaminantes, en comparación con los métodos tradicionales de producción de energía. Los interconectores, son parte crítica del ordenamiento de una celda SOFC, debido a que conecta en serie las celdas y además, separa el aire u oxígeno (cátodo) del combustible (ánodo). Por lo tanto, los requisitos del interconector son muy exigentes, por ejemplo, es necesario mantener conductividad eléctrica elevada, óptima estabilidad tanto en atmósferas reductoras como oxidantes y el coeficiente de expansión térmica (TEC), debe ser compatible con los otros componentes cerámicos de la celda SOFC. Est...

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Section: Selección De Materiales Metálicosunclassified

Avances en el desarrollo de interconectores metálicos de celdas SOFC

Alvarado-Flores¹

2013

Bol. Soc. Esp. Ceram. Vidr.

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“…The operating temperature for planar SOFC is 600-850°C, depending on the type of SOFC. At such high temperatures, two mechanisms that are associated with the interconnect material contribute to the rapid degradation of the fuel cell: increased electrical resistance caused by a growing oxide scale [5] and poisoning of the cathode caused by volatilization of the chromium(VI) species from the Cr-rich oxide scale at the interconnect surface [6][7][8][9][10]. Custom-made steels have been developed to improve oxidation resistance; however, to mitigate Cr vapourization, these steels are coated with an oxide layer that reduces Cr vapourization [9,[11][12][13].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Metallic Co-Coating Thickness on Ferritic Stainless Steels Intended for Use as Interconnect Material in Intermediate Temperature Solid Oxide Fuel Cells

et al. 2017

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The effect of metallic Co-coating thickness on ferritic stainless steels is investigated. This material is suggested to be used as interconnect material in intermediate temperature solid oxide fuel cells. Uncoated, 200-, 600-, 1000-, and 1500-nm Co-coated Sanergy HT is isothermally exposed for up to 500 h in air at 650°C. Mass gain is recorded to follow oxidation kinetics, and area-specific resistance (ASR) measurements are conducted on samples exposed for 168 and 500 h. The microstructure of the thermally grown oxide scales is characterized utilizing scanning electron microscopy and energy-dispersive X-ray analysis on broad ion beam-milled cross sections. A clear increase in ASR as a function of Cocoating thickness is observed. However, the increase in ASR, as an effect of a thicker Co-coating, is correlated with thicker (Cr,Fe) 2 O 3 scales formed on these materials and not to an increase in Co spinel top layer thickness.

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“…[8][9][10] This electrochemical reaction is not limited to the TPB, however, and can occur away from the TPB given: the formation of a continuous chromia layer for hole transport, a mixed conducting electrolyte, or a mixed conducting cathode. 8 While there is evidence for preferential electrochemical reduction of CrO 2 (OH) 2 , 11,12 open circuit chemical reactions have also been observed with cathodes containing Mn or Sr. 13 It should be noted that Cr transport to lanthanum strontium manganite (LSM) was observed via solid state diffusion, whereas vapor deposition of Cr was not observed. This has also been reported by Tucker et al, 14 who observed similar Cr transport behavior onto MnO x , except trace levels of chromium were noted to occur via vapor transport.…”

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XPS Characterization of Aluminosilicate Fibers Post Interaction with Chromium Oxyhydroxide at 100–230°C

Tatar¹,

Gannon²,

Swain³

et al. 2018

J. Electrochem. Soc.

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Chromium containing materials, e.g. stainless steels, are commonly used in high temperature (>500 • C) applications such as solid oxide fuel cell (SOFC) stacks, combustion exhaust systems, and in various chemical process equipment. At these temperatures and in oxidizing atmospheres, chromium oxide (chromia) surface layers form and grow, effectively protecting the underlying alloy. Also known to form under these conditions, however, are volatile chromium species such as CrO 2 (OH) 2 and CrO 3 . Formation of these volatile species may have detrimental effects not only on the source material, but also on surrounding materials in the system which may interact with these species. To better understand how volatile chromium species interact with materials, volatile chromium species were generated from ferritic stainless steel (FSS) T409 at 700 • C and directed into aluminosilicate fibers at 100-230 • C for 150 hours. Post exposure fibers were noted to possess yellow, brown, and/or green stained regions which were isolated and characterized using X-ray photoelectron spectroscopy (XPS). Examination of Cr 2p 3/2 peaks revealed varied Cr(VI) content and Cr(III) multiplet-split components for different discolored regions. Possible explanations for differences in chromium content by discoloration color are discussed. The volatilization of chromium species from chromium containing materials is a well-documented phenomenon which holds consequences for SOFCs, human health, and the environment. Using chromia as an example for a source, in the presence of oxygen and absence of water vapor, the dominant volatilization pathway proceeds according to Reaction 1.If, however, water vapor is present in addition to oxygen, then the dominant volatilization pathway proceeds according to Reaction 2. 1-7The generation of these gas/vapor species is well understood, but the same cannot be said of how they interact with (e.g. condense onto) other materials. This is of great importance for human health and the environment considering that chromium species may take toxic forms (hexavalent) or non-toxic forms (trivalent). This relative dearth of understanding also holds negative implications for SOFCs, and so many investigative efforts have been undertaken to understand how CrO 2 (OH) 2 interacts with ceramic components in SOFCs. Electrochemical reduction of CrO 2 (OH) 2 has often been observed to occur at the triple phase boundary (TPB), where cathode, electrolyte, and gas phase meet. [8][9][10] This electrochemical reaction is not limited to the TPB, however, and can occur away from the TPB given: the formation of a continuous chromia layer for hole transport, a mixed conducting electrolyte, or a mixed conducting cathode. 8 While there is evidence for preferential electrochemical reduction of CrO 2 (OH) 2 , 11,12 open circuit chemical reactions have also been observed with cathodes containing Mn or Sr. 13 It should be noted that Cr transport to lanthanum strontium manganite (LSM) was observed via solid state diffusion, whereas vapor deposition o...

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Effect of cathode and electrolyte transport properties on chromium poisoning in solid oxide fuel cells

Cited by 260 publications

References 77 publications

Avances en el desarrollo de interconectores metálicos de celdas SOFC

Avances en el desarrollo de interconectores metálicos de celdas SOFC

The Effect of Metallic Co-Coating Thickness on Ferritic Stainless Steels Intended for Use as Interconnect Material in Intermediate Temperature Solid Oxide Fuel Cells

XPS Characterization of Aluminosilicate Fibers Post Interaction with Chromium Oxyhydroxide at 100–230°C

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